Pressure fluid follow-up motor



Dec. 10, 1946.' A, SPENCER ET AL 2,412,366

' PRESSURE FLUID FoLLow-UP MOTQRv Filed March 19. 1942 2 Sheets-Sheej'.1

ai l

. Dec. l0, 1946. A. SPENCER ET AL- 2,412,366

PRESSURE FLUID vFOLLOW-UP MOTOR Filed March 19. 1942 2 sheets-sheet 2Patented Dec. 10, 1946 UNITED SATES PRESSURE FLUID FOLLOW-1UP MTR land,a British company Application March 19, 1942, Serial No. 435,349 InGreat Britain March 19, 1940 5 Claims. 1

This invention relates to power transmissie systems, of the repeatertype, particularly applicable to the fire control of guns, of the kindwherein movement of the gun or other object to be moved is dependentupon the relative displacement of two members, one member beingassociated with the repeater apparatus forming part of the power drivecontrolled by the signal.

The invention is primarily concerned with such electric distanttransmission systems employing two synchronous motors of the Selsyntype, one unit constituting the initiating unit or transmitter and theother unit the cancelling unit or receiver. Each unit has a three phasefield and a single phase salient two pole armature. In such a system,the units are in wired connection with a thermionic amplifier so thatthe latter is controlled in its amplifying action according to theangular displacement between the rotors of the units, the output of thethermionic amplifier being applied to a repeater motor in direct orindirect connection with the rotor of the cancelling unit, the systemincluding an hydraulic power amplier for actuating the gun or otherobject to be moved as a result of angular movement of the repeatermotor. In such a system the rotor of the initiating unit is initiallymovable through the medium of a predictor or other controllingmechanism, the output of the thermicnic amplifier and direction ofcurrent flow being respectively proportional to the angular displacementbetween the two units and the direction of displacement, movement of therepeater motor thereby taking place according to the direction ofdisplacement and in accordance with the output available from thethermionic amplifier, the repeater motor, by virtue of its direct orindirect connection with the rotor of the cancelling unit, serving tobring the rotors once more into coincidence whilst at the same timetransmitting the required motion to the gun or other object to be movedthrough the medium of the hydraulic power amplifier. Such a form ofelectric distant transmission system employing Selsyn units forms thesubject of copending application Serial No. 435,356, filed March 19,1942, whilst the hydraulic power amplier forms the subject of copendingapplication Serial No. 435,348, filed March 19. 1942, the hydraulicpower amplifier comprising an hydraulic engine preferably of theswashplate actuated type employing a control valve for varying thevolume of the supply of the fiuid medium, the torque obtainable` on theoutput shaft of the amplier being thus dependent on the position of thevalve, the valve having either a rotary motion or a combined sliding androtary movement. The invention is, however, also applicable to any otherform of electric transmission system wherein movement of the gun isdependent upon the relative displacement of two members, one memberbeing associated with the signal and the other member being associatedwith the follow-up apparatus forming part of the power drive controlledby the signal.

In such electric distant transmission systems where the movement of asignal, for example, the rotor of the Selsyn initiating unit is used tooriginate the movement of the repeater apparatus, the position-of thesignal relative to the position of the repeater apparatus must be out ofcoincidence before a movement of tht,` repeater apparatus takes place inan endeavour to restore concidence. In o-rder to maintain the velocityof the signal equal to that of the repeater appara-tus, an increase ofmis-alignment between signal and follower must give rise to a speedincrease of the follower whilst a decrease of mis-alignment mustdecrease the speed of the follower. f

The chief object of the invention is to correct automatically for anyangular lag or mis-alignment between the signal and the follower, andfurthermore to correct for any electrical lag which may occur in thesystem so as to obtain complete coincidence in the system throughout.

The hydraulic power amplifier hitherto used incorporates a differentialgear interposed between the input shaft and the main controlling valvecontrolling movement of the output shaft leading to the gun elevating ortraining mechanism. The invention consists broadly in the interpositionof a further diierential between the repeater motor and the input shaftof the hydraulic power amplier, the outer, or planet carrying, member ofthe differential being driven preferably through the medium of a furthersmall hydraulic power amplifier from the main control valve operatingshaft so as to advance the input shaft of the main hydraulic powerampli- -fier automatically and thus obtain complete col'incidencebetween the signal and follower. By

suitable correction of the gear ratio' connecting the input shaft withthe valve operating spindle this correction, may be increased, thusanticipating the electrical lag in the system.

In order that the said invention may be clearly understood and readilycarried into effect, the same will now be described more fully withreference to the accompanying drawings in which Fig. l illustratesdagrammatically the disposition of the main component parts of thesystem, Fig. 2 is a longitudinal section through the powerarnplifler-the output shaft of which is connected to the driven load,and Fig. 3 is a longitudinal section through the supplementary poweramplifier the input shaft of which is driven from the valve spindle ofthe amplifier shown in Fig. 2. Figs. 2 and 3 together correspond to Fig.1 of the before referred to application Serial No. 435,348 to whichcross reference is made for a more complete disclosure of details.

In the construction illustrated, the apparatus includes a Selsyninitiating or transmitter unit I, the rotor 2 of which represents theposition of the signal. The rotor of the Selsyn unit I is operated fromthe output shaft of a predictor or other controlling device and isconnected with a repeater electric motoru 3 through the medium of athermionic amplifier 4 and by the same means is ccnnected with thewinding of a rotor 5 of a, further Selsyn unit 6 constituting thecancelling unit o-r resetter.

The electric motor 3 through the medium of a differential gear 'I drivesthe input shaft I4 of an hydraulic power amplifier 9 which, through themedium of its output shaft Il?, serves to move a gun or other object intraining or elevation. The details of construction of this poweramplifier are shown in Figure 2.

When therrotor of the Selsyn Unit I is out of alignment with the rotorof the Selsyn unit t, current is delivered by the thermionic amplifier 4to cause angular movement of the repeater motor, in a directionaccording to the relative direction of -displacement between the twoSelsyn rotors.

The torque transmitted to the output shaft l! is under the control of avalve I2 in the hydraulic power amplifier 9, the valve I2 serving tocontrol the duantity f uid supplied to the amplier, and the opening andclosing of this valve I2 is under the control of a differential gear I3therein, shown in Fig. 2, the speed of the output shaft I0 beingdetermined by the opening of the valve and being therefore a function ofthe'angular displacement between the input shaft I4 and output shaft I0.

It will thus be seen that in accordance with the above description andignoring the function of the differential gear 1 interposed .between therepeater motor and input shaft I4, there is in the firstV case anangular displacement between the signals, that is to say, between therotor of the initiating Selsyn unit and the rotor of the Selsyncancelling unit whose shaft forms a continuation of the main shaft 8 ofthe electric motor. There is a further angular displacement between theinput shaft i4 of the hydraulic power amplifier and its output shaftlli' and this displacement increases in value with the speed ofrotation.

As a result of langular movement of the repeater motor 3, the valve I2will be partially opened, the output shaft Il) being also rotated butnot to such an extent as to obtain complete coincidence.

By the provision of the differential gear 'I between the repeater motorshaft and the input shaftV I 4 of the hydraulic power amplifier, thislack of coincidence is rectified. between the motor shaft 8 and theinput shaft I4 of the hydraulic power amplifier 9. The valve spindle Iof the valve l2 associated with the hydraulic power amplifier operatesthe input spindle I5 of a further small hydraulic power amplifier I'Iwhich is constructed and adapted to operate in the same manner as thehydraulic power amplifier 9, and is shown in 4 detail in Fig. 3. Theamplifier Il through the medium of its output shaft i8 operates thedifferential gear 1 interposed between the motor shaft 8 and input shaftIt of the main hydraulic power amplifier 9 so as to advance the inputshaft to correct for the two angular displacements hereinbefore referredto. In this way the differential gear 1 cancels the differential gear I3situated in the hydraulic power amplifier ii, thus eliminating theangular lag. The gear ratio may be so chosen that this correction alsoincludes the angular lag which exists between roto-r 2 and rotor t, thustending to reduce the angular lag between the rotor` 2 :and the outputspindle it to zero.

' The differential gears l and i3 may be of any suitable constructionand are shown diagrammatically. Referring in the first instance to thedifferential "l, driving and driven gear-wheels 2G and 2I are secured toshafts 8 and i 4, gear wheels 2l! vand 2 I meshing respectively withplanet pinions 22 and 23 which themselves intermesh, the latter beingmounted upon a planet carrier 24, the latter being in geared connectionas shown with the shaft IB. The differential gear i3 is of identical orsimilar construction, similar reference numerals being employed, thegear wheels 2t and 2l in this case being attached to shafts I4 and I0,the planet carrier 24 being in geared connection with the shaft I5.

For the purpose of understanding the differential gears if it is assumedthat the planet carriei` 24 is held stationary, and remembering thatgears 22 and 23 are in mesh with each other, and also respectively inmesh with gears 20 and 2l, it will be perceived that there is a directdrive from shaft 8 to shaft I4 which, if gears 22 and 23 are alike andif gears 2li and 2l are alike, would have a one to one relationship.Next assume that the shaft I 4 is held stationary, and it will beapparent that rotation of the gear 2i! will cause the planet carrier 24to rotate because the meshing gears 22 and 23 can walk around the gear2i. Then, it is clear that if both the gears 2l and the planet carrier24 are free to rotate there will be a different action-and as so fardiscussed the like differential gear at I3 will through the movement ofthe` planet carrier control the valve I2 to in turn control the rate ofrotation of the shaft Iii. As so far described the differential gearsintroduce their differential action which, in the case of differentialI3, is designed to control the valve I2. Returning to the differentialgear l, it is apparent that the action of the differential can bemodified by applying a control or restraint on either the shaft I4 withits gear 2| or the planet carrier 24. Here it is the planet carrier 24which is utilized, and this is done as explained by the additional poweramplifier Il operated from the shaft I5 that is driven from the planetcarrier of the differential I3, the control coming back to the shaft I8and the gear in mesh with the periphery ofthe planet carrier 24 of thedierential l.

Remembering that the electric motor 3 is under the control of theamplifier i always trying to keep the Selsyn unit 5, which is thefollow-up or cancelling unit, in step with the unit I and furtherremembering that the valve i2 is operated by the differential I3 so thatthe function of angular dis placement between the shafts I4 and I2 isdetermined by the extent of opening in valve l2 v(it is apparent thatthe component of motion of one of two differentially operable memberswill vary with the resistance to movement of the other component), itshould now be apparent that while the differential I3 wi11 introduce theangular dis placement between the shafts I4 and I5, the inherentcharacteristics of such a construction as disclosed will introduce alag. But the magnitude ofthis lag, reflected in the speed of the shaftI5, can be used to control a second differential in the same drive(remembering that shaft 3 is in alignment with shaft I4 so Idifferentiall is interposed in the shaft drive between the follow-up motor 3 and thedifferential i3), the control of the differential 1 from the planetcarrier of differential I3 being utilized to cancel the lag introducedby the differential I3.

The hydraulic power amplifiers 9 and I1 may, as aforesaid, be assumed tobe of identical construction.

Referring now particularly to power amplifier 9 (Fig. 2), rotation ofshaft IB is obtained by sliding the Valve I2 so that oil under pressurein pipe 25 passes through port 26 to actuate the pistons of theswashplate arrangement, while simultaneously the sliding movement of I2uncovers port 2l' to exhaust the oil through pipe 28. Conversely, ifhydraulic valve I2 is being slid in the opposite direction, port 2l isexposed to the pressure side and portlZS becomes the exhaust side, whilenaturally the swash plate turns the opposite direction. It will be seenthat rotation of shaft I4 via gears 24 and 29 causes the valve I 2 toslide as indicated above on account of the worm gear 35, and that at thesame time, it causes shaft I5 to rotate.

On account `of the differential gear I3, it will be noted that rotationof shaft Il! always tends to close the sliding valve I2, and thattherefore for a given load the amount of displacement of valve I2 fromits neutral posi-tion determines the speed of shaft IIB; equally theremust therefore be a displacement between shaft I4 and I0 in order torotate shaft Ii), and the higher the speed and the greater the load, thegreater valve opening is required and the greater is the angulardisplacement between I4 and I0.

It will also be appreciated that the amount of angular displacementbetween I4 and I0 is at all times reflected in a corresponding angulardisplacement of the shaft I5. As the shaft I5 is coupled to the inputspindle I6 of another but smaller hydraulic power amplifier, the shaftIS and therefore the differential gear` l, will be rotated as a functionof the rotation of I5, that is the amount of displacement from neutralposition of sliding valve I2, and that is in turn the amount ofdisplacement between shaft I4 and shaft Iii. Rotation of the shaft I8causes shaft I4 to be advanced on the position of shaft 8, andconsequently the angular lag obtaining at any moment between it and IGis thereby cancelled, so that angular displacement of the shaft 8 `givesrise to exactly similar angular displacement of shaft The abovedescription is based on the assumption that the same characteristicexists for the speed response of the repeater motor due to angulardisplacement between the rotors of the Selsyn units as for the speedresponse of the hydraulic power amplier, due to the angular displacementbetween the input shaft and output shaft. Should these characteristicsbe sufficiently different to matter in actual practiceoperation of theydifferential gear 7 can take place through the medium of cams orsimilar gearing to match the resulting characteristics. The action ofthe small hydraulic power amplifier H is irreversible for the torquesdealt with, the output shaft forming a heeling point for thedifferential gear interposed between the electric motor and the mainhydraulic torque amplifier. In practice` a controlling valve I9 isincluded in the oil outflow pipe leading from the small hydraulic poweramplifier with the object of restricting the oil flow through theamplifier and eliminating immediate response to minute rapid fluctuationof the main controlling valve in the main hydraulic power amplifier.

The dials and pointersl shown are included merely to show more clearlythe operation of the apparatus and form no part of the invention.

What we claim and desire to secure by Letters Patent of the UnitedStates is:

l. A power transmission system of the followup or repeater typeincluding a repeater motor, a hydraulic power amplier having an inputshaft, a controlling valve, and an operating shaft for said valve, and adifferential gear operated from the input shaft of the power amplifierfor operating said shaft for said valve, having in combination therewithan additional differential gear interposed between the repeater motorand said input shaft for the purpose of lag correction, said last nameddifferential gear including an outer or planet carrying member and meansdriven from said valve operating shaft for operating said member so asto advance the input shaft of said hydraulic power amplifierautomatically to obtain complete coincidence between the signal andfollower.

2. A power transmission system, as claimed in claim l, including anadditional hydraulic power amplier interposed between said valveoperating shaft of the power amplifier and the outer or planet carryingmember of the additional differential gear.

3. A power transmission system, as claimed in claim 1, said additionalhydraulic power amplier being interposed between said valve operatingshaft of the power amplifier and the outer or planet carrying member ofthe additional differential gear and including an oil supply pipe and acontrolling valve in said oil supply pipe for restricting oil flowtherethrough to thereby dampen immediate response to minute rapidfluctuation of the main controlling valve in the main hydraulic poweramplifier.

4. A power transmission system comprising a Selsyn transmitter unitoperated by the output shaft of a controlling apparatus, a Selsynreceiver unit, a thermionic amplifier in wired connection with saidtransmitter and receiver units, an electric motor in wired connectionwith said amplifier and energized by said amplifier as long as there islack of coincidence between said transmitter and receiver units, thedirection of rotation of said motor being determined by the direction ofmisalignment between the units, said electric motor being mechanicallycoupled with the rotatable part of said receiver unit to rotate thelatter until alignment is restored, an hydraulic power amplifier havinga sensitive low torque input shaft, a high torque output shaft and avalve controlling the flow of fiuid to the amplifying mechanism, adifferential gear connecting the low torque input shaft with said valveto effect its opening and closing movements and also connected with saidhigh torque output shaft, said output shaft operating the object to becontrolled, said electric motor being in driving connection with theinput shaft of the power amplier, a differential gear interposed betweenthe driving connection on said electric motor and said input shaft forthe purpose of lag correction and means driven from the operatingmechanism of said valve and connected with said last named diierental toadvance the input shaft of said amplier automatically to obtain completecoincidence between the transmitter and receiver units.

5. A power transmission system as claimed in claim 4 including anadditional hydraulic power amplifier interposed between the valveoperating mechanism of the main power amplifier and the outei' o1'planet carrying member of the additional differential and including anoil supply pipe incorporating a manually actuated controlling valve forrestricting oil ow through said additional power amplifier to therebydampen immediate response to minute rapid fluctuation of the maincontrolling valve in the main hydraulic power amplifier.

ARTHUR SPENCER.

JOHANN HERMANN ABBINK-SPAINK.

